Researchers "edit" human embryo's DNA

China has undertaken three promising experiments in this technology. But the Oregon researchers were the first U.S.-based scientists to do so, said Jun Wu, a collaborator at the Salk Institute.

Genome-changing technology that could modify a human fetus's DNA in utero to prevent deformities or diseases underwent a successful test demonstration at the University of Oregon, the MIT Technology Review reported Wednesday. The experiment, in which the researchers led by Oregon geneticist Shoukhrat Mitalipov altered human DNA in single-cell embryos, is the first of its kind in the United States.

Mitalipov and his team used the CRISPR-Cas9 genome editing technology. This method entails locating targeted genes in a cell's genome and using an enzyme called Cas9 that cuts into the strand to remove the genes. The cell recognizes that damage has occurred and induces a repair process, and the human researchers guide the repairs to make sure that new, healthier genes grow in place of the old ones.

The Oregon researchers did not invent CRISPR. But the report said that they significantly scaled it up, stating that they broke new ground "both in the number of embryos experimented upon and by demonstrating that it is possible to safely and efficiently correct defective genes that cause inherited diseases."

They also solved a problem the. Hey near studies had encountered and called "mosaicism," in which some cells in the embryo took up the desired changes but other cells did not. Mitalipov and his team injected CRISPR into the eggs at the moment when they were fertilized with sperm, and the end result was very little mosaicism